I contacted Tatchell a few months ago to ask him about the incident with Cowling and the broader issues around freedom of speech. He generously agreed to answer my questions.

Q. Why do you think freedom of speech is so important?

A. Free speech is one of the most precious of all human rights and should be defended robustly. It can only be legitimately restricted by the law when it involves harmful libels, harassment, menaces, threats and incitements to violence.

As someone who has risked life and limb for LGBT rights, how do you respond to Cowling’s accusations of transphobia and of inciting violence against transgender people?

She has produced no evidence for those preposterous claims – nor has anyone else. It is pure fabrication.

Are you disappointed in the response from the 160+ academics and activists who signed an open letter condemning you for leaking Cowling’s emails?

Those academics are part of a global network of sectarians who have been attacking me and other activists for several years. They spend more time [complaining] than fighting real racism, anti-Muslim prejudice and corporate power. Their open letter is full of the usual fabrications and unsubstantiated allegations.

What’s your opinion of the NUS policy on “no-platforming” speakers with offensive or politically incorrect views?

No-platforming should be restricted to people who incite violence, such as some far right and Islamist demagogues.

Why is it important that students listen to, engage with and debate people who hold these views?

Hateful and extremist ideas should be challenged, protested and refuted. Bad ideas are most effectively countered by good ideas backed up by rational argument and evidence. Heavy-handed legal restrictions on free speech undermine the democratic, liberal values that extremists oppose and that we cherish.

Bans and censorship don’t defeat bigotry. They merely suppress it. Whereas, exposing bigotry in open debate helps discredit and defeat it, as happened to Nick Griffin and the BNP. Bad ideas are best and most effectively defeated by good ideas.

How would you persuade student activists like Cowling, who perhaps don’t know what it’s like for people living in places such as Saudi Arabia or Zimbabwe, that free speech is worth fighting for?

Freedom of speech is one of the most precious and important human rights. It can only be legitimately restricted when someone makes false, damaging allegations – such as that a person is a rapist or tax fraudster – or when they engage in threats, harassment or the endorsement of violence.

A free society depends on the free exchange of ideas. Nearly all ideas are capable of giving offence to someone. Many of the most important, profound ideas in human history, such as those of Galileo Galilei and Charles Darwin, caused great religious offence in their time.

Generations of British people fought and suffered to secure the right to free speech. In many parts of the world people are still suffering for speaking out, including in Iran, Russia, Zimbabwe and Saudi Arabia. It is an insult to their sacrifices when students and others are so quick to suppress the free speech of others they disagree with.